1. Field of the Invention
The present invention relates to an electrophotographic method and more particularly to an electrophotographic method and apparatus for image formation with high reproducibility of gradation.
2. Description of the Prior Art
In our prior application, Japanese patent application laid open No. 14,237/1979 (U.S. Pat. No. 4,311,778) an electrophotographic method has been disclosed which enables to attain good reproduction of gradation. The range of reproducibility of original brightness (the range of reproducibility of original density) hitherto attainable by conventional electrophotographic methods was about 0.7. In contrast, according to the method proposed by the above-referred prior application, the reproducibility of original brightness can be improved to the range of 1.0 to 1.3.
However, the method has the following problem:
It includes the step of repeating the exposure of light image while gradually increasing the intensity of exposure light exposure by exposure. Because of the repeating image-wise exposure, the method requires a great deal of exposure as compared with the conventional exposure step. Therefore, to carry out the method there arises a difficulty in controlling the exposure. On the other hand, it renders very complicate the apparatus for carrying out the method.